Electromagnetic pumps are designed principally for use in liquid-metal-cooled reactor plants where liquid lithium, sodium, potassium, or sodium-potassium alloys are pumped. However, other metallic and nonmetallic liquids of sufficiently high electrical conductivity, such as mercury, molten aluminum, lead, and bismuth, may also be pumped in non-nuclear applications. The absence of moving parts within the electromagnetic pump eliminates the need for seals and bearings found in conventional mechanical pumps, thus militating against leaks, requiring less maintenance and repairs, and improving pump reliability.
An electromagnetic pump operates on the principle that the high electrical conductivity of the liquid metals being pumped allows a pumping force to be developed within the metals when the metals are confined in a duct or channel and subjected to a magnetic field and to an electric current. The duct or channel carrying the liquid metal is placed in the magnetic field and the electric current is passed transversely through the liquid metal so that the liquid metal is subjected to an electromagnetic force in the direction of the flow.
In a typical process involving molten aluminum, a float frame and a filter are floated on a molten aluminum bath in a furnace. An inlet of the pump is positioned adjacent the float frame and filter, and the pump and float frame are submerged in the aluminum bath. The buoyancy of the float frame holds the float frame against the pump inlet. As the molten aluminum is pumped, the filter removes impurities in the molten aluminum. Over time and through extensive use, the thermal effects of the molten aluminum on the float frame cause the float frame to crack. When the float frame breaks into several pieces, the float frame is unable to provide adequate buoyancy to maintain contact with the inlet and the filter will sink to the bottom of the molten aluminum bath in the furnace. When the filter is at the bottom of the furnace, it does not filter the molten aluminum and cannot be easily retrieved.
It would be desirable to develop a filtration and float apparatus and method, wherein the float frame and the filter remain buoyant when damage to the float frame occurs.